The disclosure of Japanese Patent Application No. 2002-019956 filed on Jan. 29, 2002 including the specification, drawings and abstract is incorporated herein by reference in its entirety.
1. Field of the Invention
The present invention relates generally to a fluid-filled vibration damping device capable of exhibiting a vibration damping effect on the basis of flows of a non-compressible fluid filling a fluid chamber formed therein and suitably applicable to an engine mount for use in an automotive vehicle, for example. More particularly, the present invention is concerned with such a fluid-filled active vibration damping device including: a primary fluid chamber adapted to exhibit fluid pressure variation due to a vibrational load applied thereto; and a movable rubber plate partially defining the primary fluid chamber and adapted to be displaced toward and away from an interior of the primary fluid chamber owing to its elastic deformation for regulating or controlling the fluid pressure variation induced in the primary fluid chamber.
2. Description of the Related Art
As one type of a vibration damping device to be interposed between two members of a vibration system, there is known a fluid-filled vibration damping device capable of exhibiting a vibration damping effect with the help of flows of a non-compressible fluid filling a fluid chamber formed therein. A known example of the fluid-filled vibration damping device is disclosed in JP-A-57-9340, JP-A-62-101979 and JP-A-10-184769, wherein the fluid-filled vibration damping device includes: a rubber elastic body elastically connecting a first and a second mounting member that are disposed in mutually spaced-apart relationship with each other; a primary fluid chamber partially defined by the rubber elastic body and filled with a non-compressible fluid, while being adapted to induce fluid pressure variation due to an elastic deformation of the rubber elastic body caused by a vibrational load applied between the first and second mounting members; and a movable rubber plate partially defining the primary fluid chamber such that a peripheral portion of the movable rubber plate is bonded to and fluid-tightly supported by a rigid wall portion of the primary fluid chamber so that the fluid pressure variation induced in the primary fluid chamber is regulated or controlled by displacement of the movable rubber plate owing to its elastic deformation.
The known fluid-filled vibration damping device constructed as described above is capable of moderating or eliminating the fluid-pressure variation induced in the primary fluid chamber with the help of a slight displacement of the movable rubber plate, for improving its vibration isolating effect with respect to high and small-amplitude vibrations. Alternatively, the known fluid-filled vibration damping device can exhibit an active vibration damping effect, when being arranged such that an air chamber is formed on a rear-side of the movable rubber plate, and an air pressure in the air chamber is actively controlled so as to adjust vibration characteristics of the device depending on input vibrations by regulating a spring rigidity of the primary fluid chamber. Also, the air pressure in the air chamber is actively controlled so that the movable rubber plate is actively oscillated at a frequency corresponding to that of vibrations to be damped. For the above-described advantages, the known fluid-filled vibration damping device has been applied to engine mounts, body mounts or other damping devices for use in automotive vehicles.
In the known or conventional fluid-filled vibration damping device, as described above, the peripheral portion of the movable rubber plate is bonded to and supported by the rigid wall portion of the primary fluid chamber, thereby establishing an excellent fluid-tightness of the primary fluid chamber, while preventing a relatively large amount of displacement of the movable rubber plate in its entirety. However, the conventional fluid-filled vibration damping device may suffer from inherent problems. For instance, a durability of the movable rubber plate itself may be deteriorated due to an excessively large amount of displacement of the movable rubber plate. Further, the conventional fluid-filled vibration damping device may fail to exhibit desired damping effects on the basis of flows of the non-compressible fluid, since an effective fluid pressure variation induced in the primary fluid chamber is undesirably absorbed by the displacement of the movable rubber plate, even when the vibration damping device is subjected to low and medium frequency vibrations.
To cope with the above-described problems, a modified fluid-filled vibration damping device has been proposed, as disclosed in JP-A-57-9340 and JP-A-62-101979, in which a pair of displacement limiting plates are disposed on the opposite sides of the movable rubber plate with spacing therebetween. The displacement limiting plates have a plurality of holes formed therethrough so that a fluid pressure in the primary fluid chamber can act on the movable rubber plate through the plurality of holes. Also, the displacement limiting plates can limit an amount of displacement of the movable rubber plate such that the movable rubber plate is brought into abutting contact with one of the displacement limiting plates when the amount of displacement of the movable rubber plate increases.
The proposed fluid-filled vibration damping device, however, needs the pair of displacement limiting plates to be disposed on the both sides of the movable rubber plate, thus increasing the number of components, leading to complicated or cumbersome manufacturing operations. Further, the movable rubber plate is exposed to the primary fluid chamber through the plurality of holes formed through one of the displacement limiting plates, in other words, the fluid pressure variation induced in the primary fluid chamber is transmitted to the movable rubber plate only through the plurality of holes. This means that the displacement limiting plates possibly restrict transmission of the fluid pressure variation from the primary fluid chamber to the movable rubber plate, leading to decrease in an effective pressure receiving area of the movable rubber plate. Therefore, it is difficult for the fluid-filled vibration damping device to sufficiently improve its damping capability with the help of the elastic deformation of the movable rubber plate. Yet further, the movable rubber plate and one of the displacement limiting plates cooperate to form a slight gap in the primary fluid chamber, making it difficult to remove an air remained in the gap upon filling the primary fluid chamber with the non-compressible fluid. The air remained in the slight gap formed between the movable rubber plate and the displacement limiting plate may possibly deteriorate an intended vibration damping capability of the fluid-filled vibration damping device.
It is therefore one object of this invention to provide a novelly structured fluid-filled vibration damping device including a primary fluid chamber partially defined by a movable rubber plate, which is able to effectively restrict an amount of displacement of the movable rubber plate toward and away from an interior of the primary fluid chamber by means of a simple structure with the reduced number of components, which is easy to manufacture, and which enables a fluid pressure variation in the primary fluid chamber to effectively act on the movable rubber plate for thereby exhibiting its improved vibration damping capability with the help of elastic displacement or deformation of the movable rubber plate.
The above and/or other objects of this invention may be attained according to at least one of the following modes of the invention. Each of these modes of the invention is numbered like the appended claims and depending from the other mode or modes, where appropriate, to indicate possible combinations of elements or technical features of the invention. It is to be understood that the principle of the invention is not limited to these modes of the invention and combinations of the technical features, but may otherwise be recognized based on the teachings of the present invention disclosed in the entire specification and drawings or that may be recognized by those skilled in the art in the light of the present disclosure in its entirety.
(1) A fluid-filled vibration damping device comprising: a first mounting member and a second mounting member, which are disposed in mutually spaced-apart relationship with each other; an elastic body elastically connecting the first and second mounting member and partially defining a primary fluid chamber filled with a non-compressible fluid whose pressure varies due to an elastic deformation upon application of a vibrational load between the first and second mounting members; a movable rubber plate partially defining the primary fluid chamber such that a peripheral portion of the movable rubber plate is bonded to and fluid-tightly supported by a rigid wall portion of the primary fluid chamber so that fluid pressure variation induced in the primary fluid chamber is regulated or controlled by displacement of the movable rubber plate owing to its elastic deformation, the movable rubber plate having an engaging portion; an engaging member fixedly supported by the second mounting member such that the engaging member is disposed on one of opposite sides of the movable rubber plate with a spacing therebetween to be remote from the primary fluid chamber, and is engaged with the engaging portion of the movable rubber plate so that an amount of displacement of the movable rubber plate is restricted at least in a direction toward an interior of the primary fluid chamber.
In the fluid-filled vibration damping device constructed according to this mode of the invention, the amount of displacement of the movable rubber plate can be restricted in opposite sides of the movable rubber member by only disposing the engaging member on the one side of the movable rubber plate, which side is remote from the primary fluid chamber. Therefore, no member is needed to be disposed on the other side of the movable rubber plate, i.e., in the primary fluid chamber, in order to restrict the amount of displacement of the movable rubber plate in the direction toward the interior of the primary fluid chamber. This makes it possible to provide a mechanism for restricting the amount of displacement of the movable rubber plate with the reduced number of components and with a simple structure.
That is, no member is needed to be disposed on the other side of the movable rubber plate, which is located in the primary fluid chamber, for restricting the displacement of the movable rubber plate, making it possible to directly expose a substantially entire area of a surface of the movable rubber plate to the primary fluid chamber, thereby ensuring an improved efficiency in fluid pressure transmission from the primary fluid chamber to the movable rubber member and vice versa. Thus, the fluid-filled vibration damping device is capable of exhibiting an intended vibration damping capability owing to the elastic displacement or deformation of the movable rubber plate.
Since the member to be disposed on the other side of the movable rubber plate located in the primary fluid chamber is eliminated, no gap is formed in the primary fluid chamber by the member. Thus, the fluid-filled vibration damping device of this mode of the invention never causes a conventionally experienced problem of remaining air in the gap upon filling the primary fluid chamber with the non-compressible fluid. Namely, the fluid-filled vibration damping device of this mode of the invention permits an easy and stable filling of the primary fluid chamber with the non-compressible fluid.
In order to stably restrict the amount of displacement of the movable rubber plate, the engaging member preferably comprises a rigid member supported by the second mounting member to be fixedly disposed. The engaging portion may comprise a member made of a synthetic resin material or a metallic material, which is bonded to the movable rubber plate. Preferably, the engaging portion is formed of a rubber elastic body as an integral part of the movable rubber plate. This arrangement permits elimination or attenuation of noises or vibrations, which may occur upon interface or contact between the engaging portion and the engaging member. Further, an initial state of the engagement between the engaging portion and the engaging member may be suitably determined depending upon required damping characteristics of the fluid-filled vibration damping device. For instance, the engaging portion may be opposed to an engaging part of the engaging member with a given spacing therebetween, in order to freely permit a slight amount of displacement of the movable rubber plate. Alternatively, the engaging portion may be fixedly engaged to at least one of opposite sides of the engaging member in a direction of the displacement of the movable rubber plate. While at least one of the engaging portion of the movable rubber plate is essential to practice the present invention, a plurality of engaging portions may be formed as needed. A variety of structure may be employed for supporting and fluid-tightly bonding the peripheral portion of the movable rubber plate by and to the rigid wall portion of the primary fluid chamber. For instance, the peripheral portion of the movable rubber plate may be directly bonded to the rigid wall portion of the primary fluid chamber in the process of vulcanization of a rubber material for forming the movable rubber plate. Alternatively, the peripheral portion of the movable rubber plate may be bonded to an annular fixing member, such as a metallic ring, in the process of vulcanization of the rubber material for forming the movable rubber plate, and the annular fixing member is fixedly bonded to the rigid wall portion of the primary fluid chamber by press-fitting or the like. Still alternatively, the rigid wall portion of the primary fluid chamber may fluid-tightly grip the peripheral portion of the movable rubber plate.
The engaging portion and the engaging member may have a variety of structures in engagement therebetween, provided that the engaging portion and the engaging member is able to be mutually engaged with each other in order to restrict the amount of displacement of the movable rubber plate at least in the direction toward the interior of the primary fluid chamber. For instance, the engaging portion and the engaging member have a structure in their engagement according to the following mode (2) of the invention.
(2) A fluid-filled vibration damping device according to the above-indicated mode (1), wherein the engaging member includes an engaging bore and the movable rubber plate includes an engaging projection protruding toward and extending outward of the engaging member through the engaging bore of the engaging member with a spacing therebetween, and wherein a distal end portion of the engaging projection protruding outward of the engaging member is formed as a large diameter portion whose diameter is made larger than a diameter of the engaging bore so as to function as the engaging portion such that the large diameter portion of the engaging projection is engaged with a peripheral portion of the engaging bore in order to restrict the amount of displacement of the movable rubber plate in a direction in which the engaging projection is disengaged from the engaging bore of the engaging member.
(3) A fluid-filled vibration damping device according to the above-indicated mode (2), wherein a proximal end of the engaging projection is formed as an abutting portion whose diameter is made larger than a diameter of the engaging bore so as to function as the engaging portion such that the abutting portion of the engaging projection is engaged with the peripheral portion of the engaging bore in order to restrict the amount of displacement of the movable rubber plate in a direction in which the engaging projection is inserted into the engaging bore of the engaging member. In the fluid-filled vibration damping device of this mode of the invention, the engagement between the engaging member and the engaging portion makes it possible to provide a mechanism capable of restricting the amount of displacement of the movable rubber plate in the both directions toward and away from the primary fluid chamber, with a simple structure.
(4) A fluid-filled vibration damping device according to the above-indicated mode (2) or (3), wherein the engaging projection is formed of a rubber elastic body as an integral part of the movable rubber plate. In the fluid-filled vibration damping device of this mode of the invention, the engaging projection including the large diameter portion is formed of the rubber elastic body, thus making it possible to minimize impact noises or other unsatisfactory conditions caused upon impact between the engaging projection and the engaging member, while facilitating operation for inserting the engaging projection into the engaging bore formed through the engaging member.
(5) A fluid-filled vibration damping device according to any one of the above-indicated modes (1)-(4), wherein at least a part of a portion of the movable rubber plate, which portion is remote from the engaging portion, is located to be opposed to the engaging member with a spacing therebetween, and the movable rubber plate is brought into abutting contact with the engaging member so as to restrict the amount of displacement of the movable rubber plate in a direction away from the interior of the primary fluid chamber. The amount of displacement of the movable rubber plate in the direction away from the interior of the primary fluid chamber may be restricted by the engagement between the engaging portion and the engaging member as discussed above with respect to the mode (3) of this invention. According to this mode of the invention, the movable rubber plate is brought into abutting contact with the engaging member for restricting the amount of the displacement of the movable rubber plate in the direction away from the interior of the primary fluid chamber, instead of or in addition to the engagement between the engaging portion and the engaging member. In this mode of the invention, the movable rubber plate is brought into abutting contact with the engaging member over a relatively wide area, thereby further effectively restricting the amount of displacement of the movable rubber plate in the direction away from the primary fluid chamber. Preferably, the engaging member comprises an abutting plate portion of flat-plate shape, which is disposed to be spaced apart from the movable rubber plate on the one of opposite side of the movable rubber plate remote from the primary fluid chamber, and which is provided with a plurality of through holes. In this case, the movable rubber plate is brought into abutting contact with a portion of the abutting plate portion of the engaging member where no through hole is provided, thereby restricting the amount of displacement of the movable rubber plate in the direction away from the interior of the primary fluid chamber.
(6) A fluid-filled vibration damping device according to any one of the above-indicated modes (1)-(5), wherein one of opposite major surfaces of the movable rubber plate which is remote from the primary fluid chamber, is exposed to an atmosphere, and the engaging member is disposed in the atmosphere. In the fluid-filled vibration damping device according to this mode of the invention, the engaging member is disposed in an area in which no non-compressible fluid is filled, thus eliminating the conventionally experienced problem of the remaining air in the gap formed between the movable rubber plate and the engaging member in the primary fluid chamber.
The principle of the present invention as applied to the fluid-filled vibration damping device constructed according to any one of the above-indicated modes (1)-(6) may be similarly applicable to various kinds of fluid-filled vibration damping devices as disclosed in JP-A-57-9340, JP-A-62-101979 and JP-A-10-184769. For instance, the above-described principle of the present invention may be applicable to a fluid-filled vibration damping device as disclosed in JP-A-57-9340 according to the following mode (7) of the present invention.
(7) A fluid-filled vibration damping device according to any one of the above-indicated modes (1)-(6), further comprising a flexible layer disposed on the one of opposite sides of the movable rubber plate which is remote from the primary fluid chamber so as to form an equilibrium chamber filled with the non-compressible fluid and whose volume is variable due to elastic displacement or deformation of the flexible layer, wherein one of opposite major surfaces of the movable rubber plate which is remote from the primary fluid chamber, is exposed to the equilibrium chamber, while an orifice passage is formed for permitting a fluid communication between the primary fluid chamber and the equilibrium chamber.
Similarly, the principle of the present invention as applied to the fluid-filled vibration damping device constructed according to any one of the above-indicated modes (1)-(6) may be similarly applicable to the fluid-filled vibration damping devices as disclosed in JP-A-62-101979, for example, according to the following mode (8) of the invention.
(8) A fluid-filled vibration damping device according to any one of the above-indicated modes (1)-(6), wherein the second mounting member is formed to have a generally cup shape in its entirety and is opposed at an open end portion thereof to the first mounting member with a spacing therebetween, and the elastic body is interposed between and elastically connecting the first and second mounting members such that the open end portion of the second mounting member is fluid-tightly closed by the elastic body for forming the primary fluid chamber within the second mounting member, the fluid-filled vibration damping device further comprising: a flexible layer in the form of a thin annular layer disposed outward of the elastic body with a spacing therebetween such that an inner peripheral portion of the flexible layer is bonded to the first mounting member while an outer peripheral portion of the flexible layer is bonded to the open end portion of the second mounting member, for forming an equilibrium chamber partially defined by the flexible layer, filled with the non-compressible fluid and disposed on one of opposite sides of the elastic body which is remote from the primary fluid chamber; and an orifice passage is also formed for permitting a fluid communication between the primary fluid chamber and the equilibrium chamber. This arrangement makes it possible to expose the one of opposite surfaces of the movable rubber plate which is remote from the primary fluid chamber to the atmosphere in the fluid-filled vibration damping device incorporating the primary fluid chamber and the equilibrium chamber which are held in fluid communication with each other through the orifice passage, thus eliminating the conventionally experienced problem that the vibration damping characteristics of the fluid-filled vibration damping device is adversely influenced by the air remained in the gap formed between the movable rubber plate and the engaging member in the process of filling the primary fluid chamber with the non-compressible fluid.
Also, the principle of the present invention as applied to the fluid-filled vibration damping device constructed according to any one of the above-indicated modes (1)-(6) may be similarly applicable to the fluid-filled vibration damping device as disclosed in JP-A-10-184769 according to the following mode (9) of the invention.
(9) A fluid-filled vibration damping device according to any one of the above-indicated modes (1)-(6), further comprising a fluid-tightly closed working air chamber disposed on the one of opposite sides of the movable rubber plate which is remote from the primary fluid chamber and partially defined by the movable rubber plate; and an air passageway for permitting an application of air pressure variation from an exterior area to the working air chamber. The fluid-filled vibration damping device of this mode of the invention installed in position is capable of exhibiting an active vibration damping effect by changing the air pressure variation applied to the working air chamber depending upon vibrations to be damped for adjusting wall spring stiffness of the primary fluid chamber, or alternatively is capable of exhibiting an active vibration damping effect by applying the air pressure variation having a frequency corresponding to that of vibrations to be damped to the working air chamber.